-- a variant can be created stand-alone POST /variants/:product_id for a product, or created together when the product is created variants -- list of variants dimension_combinations -- this is a required attr, the products values are the default for each variant -- a variant can be created stand-alone POST /variants/:product_id for a product, or created together when the product is created variants -- list of variants dimension_combinations -- this is a required attr, the products values are the default for each variant